You chose to play the 7 of hearts. This is correctThis will enable you to win your first Heart trick in the smaller holding, and then play back towards the larger number of Hearts in the dummy later.
Having lead the 7 of Hearts, East will play low with the 6 of Hearts, Declarer will win with the Queen of Hearts, and West will play his lowest Heart, the 3.
You will now continue with your plan of playing out the established Hearts, and Declarer will lead the 9 of Hearts, West plays the 8, Dummy plays the King, and East has to play his last Heart, which is the Jack.
Now Dummy will play the last Heart, and everyone else will discard onto it. When East is discarding, he should remember what West's opening lead was, way back in the beginning, and not throw away that suit. East will throw away the 5 of Clubs, Declarer, the 7 of Diamonds, and West, the 3 of Clubs.
Dummy has now a choice to make of which suit to play next, Spades or Clubs. However, between the two hands, there are only 2 high Spades, while there are 3 high Clubs, so Clubs seem a better option. But in both suits, there are high cards missing, that you expect to have to lose. But when you have a broken sequence of cards, if you play from the weak towards the strong, you can gamble that the missing high card is in the in-between hand. This is called a FINESSE. In the case of the Clubs, you can finesse in either direction, but since you have no clues as to which of the opponents is more likely to have the missing Queen, you might as well set up the finesse from the hand you are now in, the Dummy.
You lead the Jack of Clubs from Dummy, (and we are mentally assuming that the Queen is in East's hand) and the plan is that if West has the Queen and plays it, we will overtake with the Ace. However, if East doesn't play it, we also don't play the higher Club, but will let the trick go on the Jack and hope that West doesn't have the Queen.
So the lead is the Jack of Clubs from Dummy.
Here is East's hand:
The decision making in this move comes from East's hand, about which card to play, but there is no real advantage in not going with the suggestion, cover an honour with an honour.
20. Which card will East put on the trick?
a. Queen of Clubs
b. 6 of Clubs